According to the AirDNA website, the U.S. short-term rental supply hit record highs in 2022. That means more of your customers may be renting out their vacation homes either part time or full time. This can create numerous challenges for their property — including their septic system. Some of these challenges may require more frequent maintenance and management. Unaware property owners could irreparably damage their system if these issues are not addressed. 

The first concern is an overall increased hydraulic loading. Typically, short-term rentals through AirBnB, VRBO, HomeAway and other listing services note a maximum number of people who can sleep in the home along with the number of bedrooms and bathrooms. There are often multiple mattresses in bedrooms and pull-out sofa beds to maximize the occupancy. As occupancy increases so does general wastewater usage from toilet flushing, bathing and laundry.  

Owners should be encouraged to not exceed the typical assumption of maximum occupancy of two people per bedroom.  

PREVENTIVE MEASURES

Owners of rental properties can upgrade fixtures to reduce overall water usage. Toilets are by far the main source of water use in the home, accounting for nearly 30% of an average home’s indoor water consumption. Older, inefficient toilets use as much as 6 gpf.  Replacing old with low flow or dual flush toilets can dramatically reduce water usage to 1.6 gpf or less. The WaterSense label is used on toilets that are independently certified to meet criteria for both performance and efficiency.

Household leaks can also add a lot of extra water, and toilets are often the culprit. When toilets have a leak, it is most often due to an old or worn-out toilet flapper (valve seal). Flappers are inexpensive rubber parts that can build up minerals or decay over time. Also in the bathroom, installing low-flow showerheads and faucets can reduce the hydraulic load. Shower heads with the WaterSense label ensure these products provide a satisfactory shower that is equal to or better than conventional showerheads on the market while using 2.0 gpm or less.  

When lower-flow fixtures are installed, concentrations of contaminants will increase. When systems are sampled to determine concentrations, the overall mass loading should be considered, which takes into account both the volume and concentration of the loading. When less water is used there are also potential concerns with older building sewers and collection systems.

With less water there is greater opportunity for buildup with piping and increased likelihood of clogs. With systems that routinely plug it is best to “camera” the line to see the blockage or break to determine where it is located and determine if replacement is needed. 

Second only to bathrooms, the second biggest residential use is laundry. Older washing machines can use 40 gallons per load, while new washing machines can use as little as 10-15 gallons per load. (Look for the Energy Star label). If they have high-efficiency clothes washers, provide detergents specifically formulated for these types of machines and only use the required amount to get clothing and bedding clean which is often less than recommended, particularly with soft water.

POST INSTRUCTIONS

The second concern is peak loading of water and cleaning products.

There are two common types of short-term rentals — ones that book weekly and others that will rent for as short as one night. In either case, when one rental party leaves the entire home is cleaned top to bottom and all the laundry is typically done in a short period of time. During the COVID-19 pandemic, many rental properties increased use of anti-bacterial and disinfecting products.

Owners should be encouraged to limit the use of sanitizing products. Particularly with larger homes and large parties, the bedding and towels should be swapped out with clean ones and the laundry done at an alternate location such as a laundromat. Days with large flows have the risk of causing turbulence in the septic tank, which can cause the sludge and scum to reach downstream components.

During these high flow events the hydraulic retention time of advanced treatment systems will be reduced and soil treatment system can be overloaded. If a septic system is set up for time-dosing, alarms may go off alerting of high water levels, which renters typically ignore. 

The third concern is having renters who do not understand how septic systems work and the limitations and rules around proper use. The largest challenge is often flushing of items that do not decompose, such as sanitizing wipes, dental floss, paper towels, cigarettes, feminine products, diapers, etc. Property owners should have signs posted informing renters of proper disposal of these items in the garbage.

Another issue is the amount of food waste discharged to the system. Often with groups, large meals are prepared, adding a lot of food waste during the cooking and cleanup. Grease, oils and fats may be dumped down the drain. Owners of rental properties should not install garbage disposals, and educate renters on the proper way to discard excess food waste. 

The U.S. Environmental Protection Agency has developed outreach materials that can be used to help educate rental guests with tips on what to put (or not put) down the sink and/or drain. See www.epa.gov/septic/owners-rental-property-septic-systems/

FREQUENT INSPECTIONS

On the management and maintenance side of things, heavily used rental properties should have more frequent service visits. These visits can help alert owners of system abuse and needed maintenance before serious problems arise. On conventional systems, annual service visits are advised to measure the accumulation of sludge and scum, along with an evaluation of overall system performance. Advanced treatment systems may also need increased maintenance.